1. Field of the Invention
The present invention relates to one-time programmable (OTP) memories, and more particularly, to a more efficient system and method for programming the memories faster.
2. Related Art
The OTP memory has a gate oxide barrier that can be broken down by applying a voltage to one side of the gate. When the barrier is broken down, the resistance to the power rail (or the ground rail) becomes lower and the value is forever stored in the OTP bit. The value is either a 1 or 0.
The time required to break down the barrier and program the bit is variable depending on the fabrication process of the silicon. Some memories require a longer programming time to program a bit if the wafer process is skewed to one comer of the fabrication process. Other memories will program in shorter periods of time.
Thus, a particular problem that exists is the non-uniformity in programming time for one-time programmable memories. For example, a wafer or a particular programmable memory might have 99% of its bits that may be programmed in a fairly short time, for example, 10 μsec. However, a handful of bits are such that they require much longer programming, sometimes as long as 1 sec. For a 1K-bit programmable memory, using the lowest common denominator, or in this case, the longest possible time required to program any bit as the time to program all the bits, means that for a 1K-bit memory, 1000 seconds would be required to program it. This means that the throughput of the programming device used to program the memories is extremely low, causing an increase in the cost of manufacturing of the memories.
Tester time is costly, so a method is needed to determine the minimum amount of programming time to use on the tester.